Map size_t to usize by default and check compatibility [Rebased]

asd.fish

@@ -0,0 +1,31 @@
+for name in (rg -lF addr_of! tests/expectations | sd '.*/(.*).rs' '$1')
+    set path (fd --glob "$name.*" tests/headers)
+    if test -n "$path"
+
+        set flags (rg -F "// bindgen-flags" $path)
+        if test -n "$flags"
+            set minor (rg ".*\-\-rust\-target[ =]1.(\d+).*" $path -r '$1')
+            if test -n "$minor"
+                if test $minor -gt 47
+                    echo  $path needs to change the version from 1.$minor to 1.47
+                    sd -s "1.$minor" "1.47" $path
+                else
+                    echo $path uses version 1.$minor and that is fine
+                end
+            else
+                echo $path does not have the `--rust-target` flag
+                sd "// bindgen-flags: (.*)" '// bindgen-flags: --rust-target 1.47 $1' $path
+            end
+        else
+            echo $path does not have the flags at all
+            set contents (echo -e "// bindgen-flags: --rust-target 1.47\n"; cat $path)
+            rm $path
+            touch $path
+            for line in $contents
+                echo $line >> $path
+            end
+        end
+    else
+        echo $name headers not found
+    end
+end

src/codegen/mod.rs

@@ -836,9 +836,34 @@ impl CodeGenerator for Type {
                 }
 
                 // If this is a known named type, disallow generating anything
-                // for it too.
+                // for it too. If size_t -> usize conversions are enabled, we
+                // need to check that these conversions are permissible, but
+                // nothing needs to be generated, still.
                 let spelling = self.name().expect("Unnamed alias?");
                 if utils::type_from_named(ctx, spelling).is_some() {
+                    if let "size_t" | "ssize_t" = spelling {
+                        let layout = inner_item
+                            .kind()
+                            .expect_type()
+                            .layout(ctx)
+                            .expect("No layout?");
+                        assert_eq!(
+                            layout.size,
+                            ctx.target_pointer_size(),
+                            "Target platform requires `--no-size_t-is-usize`. The size of `{}` ({}) does not match the target pointer size ({})",
+                            spelling,
+                            layout.size,
+                            ctx.target_pointer_size(),
+                            );
+                        assert_eq!(
+                            layout.align,
+                            ctx.target_pointer_size(),
+                            "Target platform requires `--no-size_t-is-usize`. The alignment of `{}` ({}) does not match the target pointer size ({})",
+                            spelling,
+                            layout.align,
+                            ctx.target_pointer_size(),
+                        );
+                    }
                     return;
                 }
 

src/lib.rs

@@ -564,8 +564,8 @@ impl Builder {
             output_vector.push("--no-record-matches".into());
         }
 
-        if self.options.size_t_is_usize {
-            output_vector.push("--size_t-is-usize".into());
+        if !self.options.size_t_is_usize {
+            output_vector.push("--no-size_t-is-usize".into());
         }
 
         if !self.options.rustfmt_bindings {
@@ -2253,7 +2253,7 @@ impl Default for BindgenOptions {
             time_phases: false,
             record_matches: true,
             rustfmt_bindings: true,
-            size_t_is_usize: false,
+            size_t_is_usize: true,
             rustfmt_configuration_file: None,
             no_partialeq_types: Default::default(),
             no_copy_types: Default::default(),

src/options.rs

@@ -465,7 +465,12 @@ where
                 ),
             Arg::new("size_t-is-usize")
                 .long("size_t-is-usize")
-                .help("Translate size_t to usize."),
+                .help("Ignored - this is enabled by default.")
+                .hidden(true),
+            Arg::with_name("no-size_t-is-usize")
+                .long("no-size_t-is-usize")
+                .help("Do not bind size_t as usize (useful on platforms \
+                       where those types are incompatible)."),
             Arg::new("no-rustfmt-bindings")
                 .long("no-rustfmt-bindings")
                 .help("Do not format the generated bindings with rustfmt."),
@@ -975,8 +980,8 @@ where
         builder = builder.record_matches(false);
     }
 
-    if matches.is_present("size_t-is-usize") {
-        builder = builder.size_t_is_usize(true);
+    if matches.is_present("no-size_t-is-usize") {
+        builder = builder.size_t_is_usize(false);
     }
 
     let no_rustfmt_bindings = matches.is_present("no-rustfmt-bindings");

tests/headers/size_t_is_usize.h → tests/headers/no_size_t_is_usize.h

@@ -1,4 +1,4 @@
-// bindgen-flags: --size_t-is-usize
+// bindgen-flags: --no-size_t-is-usize
 
 typedef unsigned long size_t;
 typedef long ssize_t;